The center of an ellipse is located at (0, 0). one focus is located at (12, 0), and one directrix is at x = 14 1/12.
what is the equation that represents the

The standard equation for an ellipse is

where
(h,k) = coordinates of the center
a, b = semi-major and semi-minor axes

Refer to the figure shown below.
The center of the ellipse is at (0,0). 
Therefore, h=0, k=0.

One focus is at (12, 0)
Therefore
c = 12

One directrix is at  14 1/12 = 169/12.
Because the directrix is located at x = a²/c, therefore
a²/12 = 169/12
a² = 169/144
a = 13

Because c² = a² - b², obtain
b² = a² - c²
     = 169 - 144 = 25
b = 5

The equation for the ellipse is